First off I would like to thank the support staff for helping me get started. I got off to a rocky start, but they kept me on my feet and responded in a timely manner to my cries for help. I think the Fire HD presents a wonderful opportunity for budding Android developers. First, it's a great tablet, in spite of the walled garden Amazon has developed for it. I'm not a fan of walled gardens in general, but unlike some other walled gardens, however, there is [b][i]A DOOR.[/i][/b] I have told people that the only difference between a walled garden and a prison cell is that the walled garden is prettier. But since Amazon so graciously gave us an official option for installing non-Amazon Appstore apps, this walled garden is NOT a prison cell! Anyhow, back to developing for the Fire HD. The Fire HD gives budding Android developers a controlled environment for developing apps, and a fairly untapped market for selling their apps. There will undoubtedly be many millions of Fire HDs sold, and the ability to develop for one specific platform, with known capabilities and resolutions will help relatively inexperienced developers like myself avoid the complexities of developing for a myriad of different devices and capabilities until we get more experience. I bought the Fire HD for my mother, but decided to keep it a while first to make sure I could set everything up that she would need. She is currently borrowing my father's Nexus 7, and I wanted to make sure that she could do everything on the Fire HD that she likes to do on the Nexis 7. The only thing I know of that she can't do is use Talk for video chatting. So I guess Skype will have to do. In using the Fire HD, I find that even though the lack of a standard launcher cramps my style, the device is still a joy to use. I find myself reluctant to part with it. It is definitely the most stable and reliable tablet I've owned (I've had 5 other Android tablets) But what really endears the Fire HD to me is the speakers. WOW!
Yes you can install apps from unknown sources by navigating to the Setting menu on your Kindle Fire device, select "Device" option and enable "Allow Installation of Applications (From unknown sources)".